A compound represented by the general formula (1) as typified by, for example, luliconazole has an excellent antimycotic activity, and it has been pointed out that the compound may be applied to treatment of onychomycosis, which could not be treated by external administration hitherto (for example, see Patent document 1). However, in the case of producing such formulation for treatment of onychomycosis, there is a demand to further increase the content of the compound represented by the general formula (1) solubilized in the formulation. In particular, in a formulation for treatment of tinea unguium, it has been desired to solubilize the compound represented by the general formula (1) as typified by luliconazole in an amount twice or more that of a general formulation used for treatment of dermatomycosis, specifically, in an amount of 5% by mass or more, and it has been desired to develop a solvent for solubilizing and formulating the compound represented by the general formula (1) in a high concentration. However, there was a situation in which only a few solvents could be used for producing a formulation containing such compound in a high concentration because of its high crystallinity. That is, some kinds of solvents caused deficiency including crystal deposition when a low temperature condition such as 5° C. and crystal deposition during application.
In addition, in a solution of luliconazole or the like, there exists a situation in which stereoisomers are easily produced. Only crotamiton, propylene carbonate, and N-methyl-2-pyrroridone have been known as a solvent for preventing production of such stereoisomers (for example, see Patent document 2). However, such solvents may also be blended in a limited amount because of medicinal effects such as anti-inflammatory effects inherently possessed by the solvents, and it has been desired to develop a novel solvent for a formulation of luliconazole or the like as an alternative of the solvents.
where R1 and R2 each independently represent a hydrogen atom or a halogen atom, and at least one of R1 and R2 represent a halogen atom.

That is, there has been a demand to develop a solvent that enables a preparation having the following properties by means independent of solvent properties of crotamiton, propylene carbonate, and N-methyl-2-pyrrolidone (solubilization and steric stabilization properties of luliconazole or the like), in a pharmaceutical composition for external use containing luliconazole or the like in an amount of 5% by mass or more:
1) the amount of a stereoisomer of luliconazole or the like produced under a preservation condition of 60° C. for 3 weeks is 1% by mass or less with respect to the total mass of luliconazole or the like at the beginning of preservation;
2) the preparation is in a clear liquid state when preserved at a constant temperature of 20° C. immediately after manufacture.
3) no crystal is deposited when the preparation is preserved at 5° C. for 2 weeks after manufacture.
Meanwhile, acetone has been already used in an antimycotic pharmaceutical for external use, especially a pharmaceutical for external use for tinea unguium (for example, see Patent documents 3, 4 and 5). However, there has been no finding that acetone serves as a solvent for stably solubilizing luliconazole or the like while maintaining a steric structure of luliconazole or the like, in the pharmaceutical composition for external use containing luliconazole or the like.    [Patent document 1] WO/2007/102241    [Patent document 2] WO/2007/102242    [Patent document 3] JP 08-291049 A    [Patent document 4] JP 2009-511553 A    [Patent document 5] JP 2001-316247 A